1. Technical Field of the Invention
This disclosure generally relates to a semiconductor device and a method of forming the same and in particular, to a structure of a semiconductor device that protects an end of a gate line and a method of forming the same.
2. Background of the Invention
During a photo-lithography process, one of the many processes used to form a semiconductor device, the end parts of photoresist patterns become rounded due to proximity effects. As semiconductor devices become highly integrated, the pattern size is reduced and proximity effects become increasingly problematic.
FIG. 1A is a plan diagram illustrating a semiconductor device including a gate line in accordance with the conventional technology.
FIG. 1B contains cross-sectional diagrams taken along the line I-I′ and the line II-II′ respectively, of the semiconductor device of FIG. 1A. In FIG. 1B, the letter ‘aa’ indicates a region 1 that is a cross-sectional diagram taken along the I-I′ line of FIG. 1A, and the letter ‘bb’ indicates a region 2 that is a cross-sectional diagram taken along the II-II′ line of FIG. 1A.
Referring to FIGS. 1A and 1B, a field oxide (FOX) 3 is formed at a semiconductor substrate 1 to define an active region (AR). A gate oxide layer 5, a polysilicon layer 7, a tungsten layer 9, and a capping layer 11 are sequentially stacked on an entire surface of the semiconductor substrate 1. The layers 11, 9, 7 and 5 are sequentially patterned to form a gate line (GL). In a photolithography process prior to the patterning process, end parts of a photo mask (M) are orthogonal. However a plan view of the end (E) of the gate line that is subsequently formed becomes rounded as illustrated in FIG. 1A and a side view thereof becomes gently sloped as illustrated in FIG. 1B. A low-concentration impurity-doped region 4 is formed by using the gate line (GL) as an ion-implantation mask. In order to form an lightly doped drain, an insulation layer is stacked on an entire surface of the semiconductor substrate 1 and anisotropically etched to form a spacer 13 covering sidewalls of the gate line (GL). Next, a high concentration impurity-doped region 14 is formed by using the gate line (GL) and the spacer 13 as ion-implantation masks. At this time, since the side slope of the end (E) of the gate line (GL) is gentle, almost all of the insulation layer is removed to form a very thin and imperfect spacer 13 at the region 2 (bb). When a subsequent cleaning process is performed using an SC1 solution that is frequently used in a cleaning process and made of a mixture of NH4OH, H2O2 and deionized water, the SC1 penetrates the end (E) of the gate line (GL) that is weak with the thin spacer 13, thereby dissolving the tungsten layer 9. This results in reliability problems for the semiconductor device.
Embodiments of the invention address these and other disadvantages of the prior art.